1. Field of the Invention
The present invention relates to the field of optical transmission systems, and more specifically, to fiber coupling systems used to couple light between a light source and a fiber optic.
2. Prior Art
In the field of fiber optics, the coupling of light into a fiber optic using a high power, light source can result in thermal damage to the cladding of the fiber optic. The light beam input to the fiber optic defines an acceptance angle with respect to the axis of the fiber optic such that light incident upon the fiber optic at an angle exceeding the acceptance angle will not be transmitted through the fiber optic, but will radiate the housing surfaces surrounding its input end. If the energy density at the focal point of collected light is great and a sufficient amount of light is incident at an unacceptable angle, then the proximate surfaces of the housing will become hot enough to melt the cladding of the fiber optic at the contact points between the fiber optic and the housing.
In order to reduce thermal heating of the fiber optic, some coupling systems have been designed so as to protrude the input end of the fiber optic from the end of the connector that is inserted into the light source housing. In this manner, the fiber optic input end, and hence, the focal point of light at the collection face of the fiber optic, is distanced from the surfaces of the housing most likely to be irradiated. Even so, such an arrangement is not sufficient to prevent thermal damage from resulting with the use of high power, light source coupling systems in which the focal point of collected light has an energy density in the order of 30 Watts per square millimeter (using a 500 watt light source). In addition, this arrangement further requires the use of a fiber optic connector in which the input end of the fiber optic extends from the end of the connector, thereby exposing the fiber optic input end to physical damage resulting from accidental dropping or improper handling of the connector.
Other, conventional couplings have been designed to reduce thermal heating by means of surrounding the fiber optic at its input end with an insulator that thermally isolates the fiber optic and its cladding from the contact surfaces of the light source housing. Typically, this is accomplished by means of securing an insulating body (i.e., a tubular member made from ceramic or the like) around the fiber optic with an insulating adhesive such as a polymer, rubber, epoxy resin or the like. Although this is effective in inhibiting the transmission of thermal energy from the housing to the cladding of the fiber optic, a significant disadvantage exists in that the insulating adhesives utilized tend to expand and melt when exposed to high temperatures, thus causing the insulating body to crack under stress and further causing misalignment of the fiber(s) within the insulating body and the connector.